The essential basic components of a typical jet engine are a core engine embodied as a gas turbine engine, and a fan module arranged upstream of the core engine. A total intake airflow that flows through the fan module is divided into a core engine airflow that is provided into the core engine, and a bypass airflow that bypasses or flows outwardly past the core engine. Such bypass jet engines are also designated as two circuit jet engines.
As generally schematically indicated in FIG. 4, the core engine includes at least one compressor, at least one combustion chamber, and at least one turbine. Typically, the core engine includes two compressors arranged flow-upstream from a combustion chamber, as well as two turbines positioned flow-downstream from the combustion chamber. More particularly, the two compressors include a low pressure compressor and a high pressure compressor, and the two turbines include a high pressure turbine and a low pressure turbine. The rotors of the high pressure compressor and the high pressure turbine are connected by a first shaft, while the rotors of the low pressure compressor and the low pressure turbine are connected by a second shaft. The two shafts are arranged concentrically or coaxially, i.e. with one shaft nested inside the other shaft. Other conventional engines are known, which additionally include an intermediate pressure compressor and an intermediate pressure turbine, of which the respective rotors are connected by a further shaft.
It is generally known in practice, in such conventional two circuit jet engines, that the fan is driven to rotate in a direction opposite or contrary to the rotation direction of the low pressure compressor. In that regard, the low pressure compressor is driven directly by the low pressure turbine via the second shaft, while the fan is driven by the low pressure turbine through an interposed transmission. Still further, a so-called bearing star or spider is arranged between the fan and the low pressure compressor in order to support and rotatably bear the fan. As a result, in the conventional arrangement, the fan is positioned at a considerable spacing distance flow-upstream from the low pressure compressor. The low pressure compressor itself typically comprises several compressor stages.
The above described general construction concept for a conventional two circuit jet engine is characterized by a relatively long structural configuration. This is at least partially due to the significant spacing distance between the fan and the low pressure compressor, whereby the low pressure compressor is further embodied with multiple stages. These features leading to a large structural length of the jet engine further bring about a high total weight of the engine and impair or reduce the operating efficiency thereof.